I'd just like to say that anyone wanting a true "Free Roam" mode, with the ability to save any time you want should really get the Jimmy's Vendetta DLC, because it is exactly that. Yeah, it kind of sucks that you have to pay $10 for that, but the story missions and extra story are also very fun, it is worth the $10.
Rig1: System Specs.
Rig2: A8-5600K@4.4GHz / AsRock FM2A75 Pro4 / 8GB Corsair DDR3-1600 9-9-9-24 / HD7560D / Samsung DVD-Burner / 1.5TB WD Green + 3x3TB WD RED in RAID5
Rig3: Athlon X2 4200+ / M4A79 Deluxe / 4GB G.Skill Pi DDR2-800 4-4-4-12 / GT430 / Sony DVD-Burner / 500GB WD
Rig4: Phenom II x6 1605T @ 3.6GHz / Asus M5A99X Evo / 8GB PNY DDR3-1600 9-9-9 / GTX470 & GTX470 / Samsung DVD-Burner / 1.5TB Seagate